On Tue, Mar 30, 2021 at 06:15:20PM +0800, Muchun Song wrote:
> We already have a helper lruvec_memcg() to get the memcg from lruvec, we
> do not need to do it ourselves in the lruvec_holds_page_lru_lock(). So use
> lruvec_memcg() instead.
>
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> ---
> include/linux/memcontrol.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index a35a22994cf7..6e3283828391 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -744,20 +744,20 @@ static inline struct lruvec *mem_cgroup_page_lruvec(struct page *page)
> return mem_cgroup_lruvec(memcg, pgdat);
> }
>
> +static inline struct mem_cgroup *lruvec_memcg(struct lruvec *lruvec);
Please reorder the functions instead to avoid forward decls.
> static inline bool lruvec_holds_page_lru_lock(struct page *page,
> struct lruvec *lruvec)
> {
> pg_data_t *pgdat = page_pgdat(page);
> const struct mem_cgroup *memcg;
> - struct mem_cgroup_per_node *mz;
>
> if (mem_cgroup_disabled())
> return lruvec == &pgdat->__lruvec;
>
> - mz = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
> memcg = page_memcg(page) ? : root_mem_cgroup;
>
> - return lruvec->pgdat == pgdat && mz->memcg == memcg;
> + return lruvec->pgdat == pgdat && lruvec_memcg(lruvec) == memcg;
Looks reasonable to me, but I wonder if there is more we can do.
lruvec_memcg() already handles CONFIG_MEMCG and mem_cgroup_disabled()
combinations, and there is also a lruvec_pgdat() which does.
One thing that is odd is page_memcg(page) ? : root_mem_cgroup. How can
lruvec pages not have a page_memcg()? mem_cgroup_page_lruvec() has:
memcg = page_memcg(page);
VM_WARN_ON_ONCE_PAGE(!memcg && !mem_cgroup_disabled(), page);
Unless I'm missing something, we should be able to have a single
definition for this function that works for !CONFIG_MEMCG,
CONFIG_MEMCG + mem_cgroup_disabled() and CONFIG_MEMCG:
lruvec_holds_page_lru_lock()
{
return lruvec_pgdat(lruvec) == page_pgdat(page) &&
lruvec_memcg(lruvec) == page_memcg(page);
}
